Cocaine use and its associated risky sexual behaviors (e.g., sex with multiple partners, inconsistent condom use, trading sex for drugs or money) represent a significant contributor to the ongoing spread of HIV. However, little is known about how sex, drugs, and money are valued in this population, nor about the perturbed neural processes mediating these tradeoffs. In this application, we directly address the objective of PAS-07-324 to increase understanding of processes of cocaine addiction that influence decisions about high-risk sexual behavior. We propose to explore this via the convergence of behavioral and neural underpinnings of the pathological decisions made by Chronic Cocaine Users (CCUs) not in treatment using a model-based approach, behavioral decision tasks, and functional magnetic resonance imaging (fMRI). Our overall hypothesis is that the processes of addiction result in a dysfunctional decision system that underlies the risky sexual behavior engaged in by CCUs;in other words, CCUs engage in risky sexual behavior because they discount future outcomes as a result of a hypoactive executive system (in prefrontal cortex) and a hyperactive impulsive system (in limbic brain circuits). To improve our understanding of cocaine addiction processes that influence decisions about risky sexual behavior, we will obtain critically needed information about the CCU's valuation of relevant commodities (sex, drugs, money), recognizing that these commodities serve multiple functions and may interact with one another in novel ways. We will study valuation and inter-temporal choice within and across different commodities to gain new insights into the decisions made by CCUs, including decisions closely tied to the high-risk behavior of trading sex for drugs or money, and how they differ from Recreational Cocaine Users (RCUs) and Community Control Participants (CCPs). We hypothesize that different commodities will show different profiles of effect depending on availability of other commodities (same or different commodities), their temporal location (immediate or later), and the subject group (CCUs, RCUs, CCPs). Additionally, given the existing data, we anticipate systematically replicating that the discounting of money (money now vs. later) will be predictive of HIV risk behavior in a new population (CCUs). The inclusion of neural correlates will permit us to identify for the first time the role of different neurobehavioral decision systems in decision making predictive of HIV risk behavior. By comparing money discounting to discounting of drug and sexual activity within and across commodities, we will determine whether novel discounting procedures and associated neural processes are more predictive of risky behavior than money discounting. Completion of this project will provide substantial new information about neural valuation systems that are altered by addiction and lead to risky sexual behavior. Understanding how the commodities of interest interact with one another and the neural systems that participate in that valuation may suggest new approaches to alter the pathologic valuation and impact risky behavior associated with the spread of HIV. PUBLIC HEALTH RELEVANCE: Completion of this project will provide new information about stimulant addiction and associated risky sexual behaviors that have been shown to contribute to the spread of HIV. By examining the regions of the brain that underlie an addict's perturbed decision making, we expect our data to result in treatment applications. We believe that greater understanding of the mechanisms that alter an addict's valuation of commodities like sex, drugs, and money could lead to new approaches to altering the pathologic decision making, thus reducing the correlated risky behaviors associated with the spread of HIV.